Apparatus, system, and method for convectively and evaporatively cooling a body

ABSTRACT

An apparatus is disclosed for convectively and evaporatively cooling a patient. The apparatus comprises an upper sheet and a base sheet that are attached at a plurality of locations to form a convective device. The base sheet includes a plurality of apertures that direct an inflating medium from the convective device toward the patient. The base sheet also supports a fluid delivery apparatus that distributes and delivers a cooling fluid to the patient. The fluid is evaporated from the patient&#39;s skin by the inflating medium exhausted from the convective device. The fluid delivery apparatus may be constructed in a variety of configurations and may circulate a variety of fluids, which may be pressurized or unpressurized. In operation, an air blower, that may also include a compressor for selectively delivering room temperature or cooled air to the appatatus, is connected to the convective device. The blower delivers air, under pressure, to an inlet opening in the convective device. The pressurized air is distributed throughout the convective device and flows to the patient through the apertures in the base sheet. The apparatus is configured to cover one or more portions of a patient&#39;s body. In one construction, the apparatus covers all of the patient&#39;s body except for the head. In an alternative construction, a specially designed apparatus is constructed to cover only the patient&#39;s head.

This application is a continuation of U.S. patent application Ser. No.09/176,477, filed Oct. 20, 1998, which is a continuation of U.S. patentapplication Ser. No. 08/918,308, filed Aug. 26, 1997, now U.S. Pat. No.5,860,292.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to convective devices such as thermalblankets used in a medical setting to deliver a bath ofthermally-controlled gaseous medium, such as air, to a patient.

2. Description of the Related Art

Thermal blanket prior art is disclosed in commonly-assigned U.S. Pat.No. 4,572,188 entitled “AIRFLOW COVER FOR CONTROLLING BODY TEMPERATURE”and U.S. Pat. No. 5,405,371 entitled “THERMAL BLANKET”. These twopatents describe thermal blankets which include a plurality ofcommunicating inflatable chambers. In these blankets, apertures areformed through blanket base sheets. These apertures open through thebase sheets into the chambers. When inflated with warmed air, thepressure of the air in the chambers causes the air flow cover toinflate. The apertures exhaust the warmed air through the base sheets,and the warmed air is contained between the base sheets and thepatients. Therefore, these thermal blankets create an ambientenvironment about the patient, the thermal characteristics of which aredetermined by the temperature and pressure of the gaseous inflatingmedium.

Temperature control in humans has important medical consequences. Thehuman body has evolved over several million years to maintain its coretemperature within a very narrow range. Thermoregulatory responses suchas vasoconstriction, vasodilatation, shivering or sweating occur inresponse to core body temperature changes as small as +/−0.1° C. Humancellular functions, biochemical reactions and enzymatic reactions areoptimized within this narrow temperature range.

The prior art thermal blankets address the problem of warming a patientin order to treat hypothermia (a core temperature that is less thannormal) such as might occur operatively or post-operatively. Thesethermal blankets have proven themselves to be extremely useful andefficient in the treatment of patients whose core body temperaturesmight otherwise become undesirably low either during or after a medicalprocedure, such as surgery.

However, there are circumstances under which a patient should be cooledrather than warmed in order to treat hyperthermia (a core temperaturethat is greater than normal). Hyperthermia may result from environmentalheat stress or from illness. Otherwise normal individuals may sufferhyperthermia when their natural cooling mechanisms, such as sweating,are overwhelmed during heavy physical work in a hot environment. This isusually associated with relatively inadequate fluid consumption thatresults in inadequate sweating. Heat stress disorders, categorized inascending order of severity, include: heat cramps, heat syncope, heatexhaustion and heat stroke. Normally, a person will voluntarily stopworking well before the onset of heat exhaustion, but competitiveathletes or military personnel may push themselves beyond this limit.

Hyperthermia may also be caused by fever associated with illness. Suchfever has many causes, including: infection, tumor necrosis, thyroidstorm, malignant hyperthermia or brain injury. Brain injuries that causehyperthermia usually involve the hypothalamus, and may be caused bytumors, stroke, head injury or ischemic brain injury due to cardiacarrest.

The physiologic consequences of hyperthermia span a spectrum of severitywith fluid and electrolyte imbalances, increased cellular metabolicrates, and cognitive impairment being at the low end. In themid-spectrum, motor skill impairment, loss of consciousness and seizuresoccur. At the high end, the individual suffers irreversible cellularinjury, especially of the highly metabolic brain and liver cells, andthen finally organ failure and death. Hyperthermia is a thus a conditionthat, depending on its severity, may require immediate cooling treatmentto return the patient's core temperature to normal.

Cooling treatment may also have other important uses. There is a growingbody of evidence suggesting that in some situations, mild-to-moderatehypothermia may provide beneficial protection against injury. Theprotective benefit of hypothermia has been shown when the blood flow toall or part of the brain is interrupted. Brain ischemia due to aninterruption of the blood flow may occur during cardiac arrest, surgeryon the blood vessels of the brain, stroke, traumatic brain injury oropen heart surgery. Cooling the brain before or in some cases afterthese events occur seems to be protective, and decreases the severity ofthe ultimate brain damage.

Various apparatus and techniques have been used over the centuries tocool the human body. Cooling technologies can be generally categorizedas: conductive, convective, or evaporative. While many technologies havebeen tried, all are limited in the clinical setting by lack ofpracticality, difficulty of use, ineffectiveness, and/or excessive powerconsumption.

Conductive cooling is very effective when accomplished by packing ahyperthermic person in ice, or immersing the person in cool, or evencold, water. While ice is an effective cooling agent, it is painful tothe patient, can damage the skin, is frequently not available in largequantities, and is not practical for long term use. Water baths are alsoeffective, but not practical for the comatose or intensive care patient,or for long term use. A less effective, but commonly used, method ofconductive cooling involves placing the person on, and/or under, a coldwater circulating mattress and/or cover. These devices have chamberswith circulating water therein. The water cools the surfaces of thedevice, which in turn removes heat from the patient wherever thesurfaces thermally contact the patient's skin. These devices aregenerally uncomfortable and heavy, and their thermal contact isfrequently inefficient because they are not precisely shaped to the bodysurface.

Convective cooling consists of blowing room temperature air, or cooledair onto the patient. Convective cooling is the least effective methodof cooling, from a thermodynamic point of view. Room temperature air canbe blown very inexpensively with a fan. However, its coolingeffectiveness is severely limited if the patient is not sweating. Cooledair can be made with a traditional compression or heat-pump airconditioner, or with thermoelectric cooling. Cooled air has also beengenerated for centuries using the so-called “swamp cooler” principle ofvaporizing water into the air stream. The water evaporates into the air,thus cooling the air. The cooled air is then applied to a person.

An example of such a cooler is shown in U.S. Pat. No. 5,497,633 entitled“EVAPORATIVE COOLING UNIT” by Jones et al. Once the air is cooled by anyof these technologies, it can be delivered to a person by generallycooling the environment around the person, such as cooling the air in aroom. For more efficient convective cooling utilizing less energy, thecooled air can be delivered to a person more effectively by confiningthe cooling to only the person. This can be accomplished using aconvective thermal blanket such as shown in U.S. Pat. No. 4,572,188 or5,405,371, referred to above and incorporated herein by reference.Another convective thermal blanket is shown in U.S. Pat. No. 4,777,802entitled “BLANKET ASSEMBLY AND SELECTIVELY ADJUSTABLE APPARATUS FORPROVIDING HEATED OR COOLED AIR THERETO” by Feher. Confined convectivecooling has also been shown in the form of a jacket-like device in U.S.Pat. No. 5,062,424 entitled “PORTABLE APPARATUS FOR RAPID REDUCTION OFELEVATED BODY CORE TEMPERATURE” by Hooker.

Convective cooling removes the stress of environmental heat, but isminimally effective in active cooling. This limited thermodynamiceffectiveness is particularly evident when trying to cool patients withfevers. Generally, in order to be cooled by convection, the patientsmust be anesthetized and paralyzed to prevent heat producing shivering.Further, the thermodynamic inefficiency of convective cooling causesthis method of cooling to use considerable electrical power and generateconsiderable waste heat, both of which can be a problem in the emergencyor intensive care situation.

Evaporative cooling is the thermodynamic basis of the highly efficientsweating response. Each gram of water that evaporates extracts 540calories of heat from the skin of the body being cooled. Because of thevery large heat of vaporization of water, large amounts of heat areremoved from the body by evaporating relatively small amounts of water.Evaporative cooling has been practiced since the beginning of mankind,simply by wetting the skin or clothing, and letting the wetting agentevaporate. Evaporative cooling is used even today in hospitals, in theform of sponge baths, where the patient is wetted with water, andallowed to dry by evaporation. Sometimes a fan will be blown on thepatient to increase the rate of evaporation. While this method ofcooling is clearly effective, it is labor intensive, messy, requires thepatient to be totally exposed, and is generally not practical forprolonged cooling. Finally, the effectiveness of evaporative cooling isseverely limited in high humidity environments.

Therefore, there is a need for a temperature control device, andparticularly a thermal blanket, that can accommodate a patient whorequires treatment for hyperthermia or requires cooling as an injuryprevention mechanism. What is required is an inexpensive covering thatcools a patient rapidly and efficiently in a clinical setting, yet whichmay be easily and conveniently used by medical personnel.

SUMMARY OF THE INVENTION

In accordance with certain objectives of this invention, and to overcomethe limitations of the prior art, an apparatus is provided thatcompounds convection with evaporation to cool a patient The apparatusincludes an inflatable thermal blanket including an upper sheet and abase sheet that are attached at a plurality of locations to form aninflatable structure. The base sheet includes a plurality of aperturesthat exhaust an inflating medium from the inflatable structure towardthe patient. An air blower that may also include a compressor forselectively delivering room temperature, or cooled, air to the thermalblanket, delivers air, under pressure, to an inlet opening in theinflatable thermal blanket. The pressurized air is distributed withinthe inflatable structure, and flows to the patient through the aperturesin the base sheet. The base sheet supports a fluid delivery element thatdirects a cooling fluid onto the patient. The fluid is evaporated by theinflating medium exhausted from the inflatable structure. The fluiddelivery element may be constructed in a variety of configurations andmay circulate a variety of fluids, which may be pressurized orunpressurized.

The inflatable thermal blanket is configured to cover one or moreportions of a patient's body. In a first preferred embodiment, thethermal blanket covers all of the patient's body except for the head. Inan alternative embodiment, a specially designed thermal blanket isconstructed to cover only the patient's head.

It is therefore a primary object of the invention to provide aconvenient, inexpensive and effective means for rapidly cooling a body(human or animal).

It is a further object of the invention to provide a device for coolinga body both convectively and evaporatively.

It is a further object to provide such cooling in an inexpensiveinflatable thermal blanket which can be used with existing inflatablethermal blanket equipment.

The foregoing, together with other objects, features and advantages ofthis invention, will become more apparent when referring to thefollowing specification, claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

For a more complete understanding of this invention, reference is nowmade to the following detailed description of the embodiments asillustrated in the accompanying drawing, wherein:

FIG. 1 is a perspective view of a patient and an inflatable thermalblanket according to the invention, deployed with forced-air pump thatsupplies air to the thermal blanket, and a fluid supply system fordelivering an evaporative cooling fluid to the thermal blanket;

FIG. 2 is a partial cross-sectional view taken through an inflatableportion of the inflatable thermal blanket of FIG. 1;

FIG. 3 is a diagrammatic cross-sectional view of the patient andinflatable thermal blanket of FIG. 1, showing one alternative lateralplacement arrangement for components of a fluid delivery apparatus;

FIG. 4 is another diagrammatic cross-sectional view of the patient andinflatable thermal blanket of FIG. 1, showing another alternativelateral placement arrangement for components of a fluid deliveryapparatus;

FIG. 5 is a bottom view of the inflatable thermal blanket of FIG. 1,showing one alternative two-dimensional placement for components of afluid delivery apparatus and also showing one alternative manifoldtherefor;

FIG. 6 is a bottom view of the inflatable thermal blanket of FIG. 1,showing another alternative two-dimensional placement for components ofa fluid delivery apparatus and also showing another alternative manifoldtherefor;

FIG. 7 is a bottom view of the inflatable thermal blanket FIG. 1,showing another alternative two-dimensional placement for components ofa fluid delivery apparatus and also showing another alternative manifoldtherefor;

FIG. 8 is another diagrammatic cross-sectional view of the patient andinflatable thermal blanket of FIG. 1, showing additional componentswhich may be used in the inflatable thermal blanket;

FIG. 9 is a perspective view of a patient and an inflatable thermalblanket, and also illustrates a forced-air pump for supplying air to theinflatable thermal blanket, and an alternative fluid supply apparatusfor delivering an evaporative cooling fluid to the inflatable thermalblanket;

FIG. 10 is a side view of a patient and inflatable thermal blanket forconvectively and evaporatively cooling a patient's head;

FIG. 11 is a cut-away side view of the inflatable thermal blanket ofFIG. 10 showing construction details thereof; and

FIG. 12 is a cut-away plan view of the patient and inflatable thermalblanket of FIG. 10 showing additional construction details thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention is represented by embodiments set forth in the followingdescription, and illustrated in the figures, in which like numbersrepresent the same or similar elements. While this invention isdescribed in terms of an exemplary embodiment, it will be appreciated bythose skilled in the art that variations may be accomplished in view ofthese teachings, without deviating from the spirit or scope of theinvention.

Effective patient cooling in a clinical setting is achieved by providingan inflatable thermal blanket that joins an air delivery system forproviding a convective cooling component with a fluid delivery apparatusfor providing an evaporative cooling component. It has been found thatcombining evaporative cooling with convective cooling with an inflatablethermal blanket dramatically increases the cooling effectiveness of theconvective cooling, while making the evaporative cooling convenient andpractical, even for prolonged use. The inflatable thermal blanketsdisclosed herein maximize the positive features of convective andevaporative cooling while minimizing the negative features of each.

FIG. 1 illustrates a patient 100 in a prone position on an examinationor operating table 102. The table 102 may be in doctor's office, in anout-patient facility associated with a hospital facility, or any othersuitable location. The patient 100 is ill with his head 104 andshoulders 106 lying flat and supported on the table 102 (along with theremainder of the patient's body). As shown in FIGS. 3 and 4, thepatient's arms 110 lie at the patient's side.

An inflatable thermal blanket indicated by reference numeral 120, andhaving convective cooling and evaporative cooling components, is showncovering all of the patient's body, except for the head 104 andshoulders 106. The inflatable thermal blanket 120 includes an inflatablesection 130 surrounded by a non-inflatable section that includes a footdrape 140 and side edges 150. A head drape could also be provided, ascould one or more non-inflatable recesses in the inflatable portion 130to facilitate unrestricted viewing of, and access to, selected areas ofthe patient 100.

Further, FIG. 1 is not meant to suggest limitation of the invention toan inflatable thermal blanket that covers substantially all of apatient's trunk and limbs. It could also be embodied in an arrangementthat uses an inflatable thermal blanket that is shaped and deployed overportions of the patient's body, as well as over one, or fewer than allof the patient's limbs. In this regard, for example, reference is givento U.S. Pat. No. 5,405,371, which describes inflatable thermal blanketsthat cover the outstretched arms and upper chest, and the lowerextremities of a person. Other configurations are illustrated in U.S.Pat. Nos. 5,300,101; 5,324,320; 5,336,250; and 5,350,417.

Returning to FIG. 1, the inflatable section 130 includes an inlet 160through which a flow of temperature-controlled air is received toinflate the inflatable thermal blanket. The flow of air is provided byan airhose 162 from a forced-air unit 164. The forced-air unit 164minimally includes a blower system powered by an electric motor or thelike for delivering a flow of air. The blower system preferably hasvariable air speed control capability and may have air temperaturecontrol capability. Optionally, for additional cooling effectiveness,especially in hot and humid environments, an air cooling unit ordehumidifying unit could be included in the forced-air unit.Alternatively, the air cooling unit or dehumidifying unit may beseparate from the forced-air unit, in which case it could be interposedbetween the forced air-unit and the airhose 162. Cooled air increasesthe efficiency of the convective cooling component of the blanket 120.Dehumidified air increases the efficiency of the evaporative coolingcomponent of the blanket. Cooled, dehumidified air therefore optimizespatient cooling.

The inlet 160 in the inflatable section 130 may be provided with a cuffor other conventional connector adapted to receive and retain a nozzle163 of the airhose 162. Using this configuration, pressurized air canflow through the airhose 162 into the inflatable section 130.

The inflatable thermal blanket 120 of this invention may be constructedby modifying a commercially available inflatable thermal blanket of thetype which is known in the art, including BAIR HUGGER® Thermal Blanketsfrom Augustine Medical, Inc., Eden Prairie Minn. Alternatively, theinflatable thermal blanket 120 could be constructed using methods andmaterials that are known for making similar products. One example ofconstruction details suitable for making the inflatable thermal blanketof this invention is found in commonly-assigned U.S. Pat. No. 5,405,371.

With reference now to FIGS. 1 and 2, the inflatable thermal blanket 120is assembled from a base sheet 200 having a laminated structure in whicha bottom layer 210 comprises a fibrous, preferably non-woven, structurecomposed of synthetic or natural materials. A top layer 211, comprisinga sheet of synthetic material, is disposed on and laminated to a surfaceof the bottom layer 210. For example, the bottom layer 210 may be anon-woven, hydroentangled polyester material and the top layer mayinclude a polypropylene film that is extrusion-coated on to thepolyester layer. According to a first alternative, the bottom layer 210may comprise a non-woven, paper-based material to which a top layerincluding either a polyethylene or a polypropylene film has been gluelaminated. According to a second alternative, the bottom layer maycomprise a single layer of fibrous material. To form an inflatablestructure that may include one or more inflatable chambers 220, an uppersheet 215 of material is attached at a plurality of locations to the toplayer 211. Preferably, the upper sheet 215 comprises the same materialas the top layer 211 of the base sheet 200. The upper sheet 215 isattached to the top layer 211 in the preferred embodiment in acontinuously-running web process that includes stations at which theupper sheet 215 is heat-bonded to the top layer 211 to form theinflatable and non-inflatable sections of the inflatable thermal blanket150. The inflatable chambers 220 are shown in FIGS. 1, 3 and 4 as havinga generally elongate tubular shape, although such chambers and shapesare not necessary to the invention The inflatable chambers 220 areformed by discontinuous elongate heat seals extending longitudinallyalong the blanket 120. FIGS. 3 and 4 show a cross-sectional view of theelongate heat seals. These heat seals are shown as having sealedportions 221 and unsealed portions 227. At the sealed portions 221 ofthe discontinuous elongate heat seals, the top layer 211 of the basesheet 200 is bonded to the upper sheet 215 in an elongate, airimpermeable seam. Where the discontinuities 227 occur, air may circulatelaterally between the inflatable chambers. These discontinuities providecommunication between the inflatable chambers, permitting pressurizedair to circulate from the inlet 160 to, and through, the inflatablechambers 220. It should be understood that the inflatable structurecould be formed by a plurality of stake-point seals, or by longerelongate seals. The plurality of apertures 217 that open through thebase sheet 200 exhaust pressurized air from the inflatable chambers 220underneath the inflatable thermal blanket 120 to bathe the patient 100in a cooling ambient atmosphere.

Continuous, air impervious seals 230 are shown in FIGS. 1, 3 and 4 alongthe sides of the inflatable thermal blanket 120. Continuous, airimpervious seals 232 and 234 also extend transversely at the foot endand the head end of the blanket 120, respectively. These seals form theone or more uninflatable sections of the inflatable thermal blanket 150.These uninflatable sections function essentially as drapes that maintainan ambient atmosphere beneath the inflatable thermal blanket. As FIGS.1, 3 and show, there are two, parallel continuous, air-impervious edgeseals 230 that are near the respective sides of the inflatable thermalblanket and two continuous, air-impervious end seals 232 and 234 ateither end of the inflatable thermal blanket. The perimeter of theinflatable thermal blanket 120 is therefore sealed by a continuous,air-impervious seal comprising the seals 230, 232 and 234.

The invention further includes an evaporative cooling element comprisinga fluid distribution apparatus. The fluid distribution apparatusdistributes fluid over, and delivers it to, various areas, portions, orlimbs of a patient's body. The fluid distribution apparatus includes oneor more fluid delivery channels or conduits 250 mounted to the undersideof the base sheet 200. Preferably, the conduits 250 are attached to theinflatable thermal blanket 120 in areas of the blanket that correspondto areas of the patient's body that are to be evaporatively cooled. InFIG. 1, the conduits 250 are shown extending from the patient's chestarea to the patient's lower legs. In FIG. 3, the conduits 250 areattached to the underside of the inflatable thermal blanket 120 belowcentral portions of the inflatable section 130. In FIG. 4, the conduits250 are attached to the underside of the inflatable thermal blanket 120below the discontinuous elongate heat seals. One example of a fluidconduit would be a length of approximately ⅛ inch internal diameter PVCtubing, similar to standard IV (intravenous) tubing.

The fluid conduits 250 deliver fluid to the patient 100 through aplurality of orifices 252, which are formed intermittently along thelength of each conduit in the walls thereof. The orifices 252 allowfluid to be delivered to a selected area or areas of the patient 100. Asshown in FIG. 3, the orifices 252 may be holes, or they may be slits, orany other type of perforations that allow the fluid to pass through thewall of the conduits 250, and be deposited onto the body surface below.Alternatively, as shown in FIG. 4, the orifices may be formed as nozzles254 that allow the fluid to be sprayed through the wall of the conduits250, on the body surface below. Additionally, the orifices 252 mayinclude openings 256 in the ends of the conduits 250.

As shown in FIG. 1, the fluid distribution apparatus includes a fluidreservoir 260 connected to the conduits 250, via an inlet line 262, andan inlet manifold 264. The fluid reservoir 260 is preferably acollapsible plastic bag, identical to the currently-used IV fluidcontainers. Alternatively, bottled fluid or a continuous supply from awater system could be used. The inlet line 262 is preferably made fromfluid supply tubing such as standard IV tubing with standard Luerconnectors at each end. A valve 266 is provided in inlet line 262 toallow an operator to control the flow rate of the fluid. The inletmanifold 264, which distributes fluid among the conduits, can be formedin a variety of ways.

FIG. 5 illustrates the inlet manifold as a Y-connection coupler 270 thatis attached, at its upstream side, to the end of the inlet line 262.FIG. 5 also illustrates an alternative pattern for the conduits 250, inwhich two conduits 272 and 274 made from small bore plastic tubing areattached to the downstream side of the coupler 270. These conduitsextend from the upper side of the inflatable thermal blanket 120 to theunderside thereof through respective holes 276 and 278 that are formedin adjacent ones of the seals that join the upper and base sheets of theinflatable thermal blanket 120. The conduits 272 and 274 are attached tothe underside of the inflatable thermal blanket 120 in a serpentinepattern. In the configuration shown in FIG. 5, the orifices 280 of theconduits are oriented to wet the entire body of the patient 100 exceptthe head area. It should also be understood that the conduits could beoriented to wet only selected parts of the body. As shown in FIG. 5, thenumerous air apertures 217 will direct evaporative air to all portionsof the patient's body where fluid is delivered by the conduits.

FIG. 6 illustrates an alternative construction for an inlet manifold andfluid delivery conduits. In this construction, the inlet manifold is alinear length of tube 290 mounted to the underside of the blanket 120.The inlet line 262 extends through a hole formed in a seal, and attachesto a coupler 292 that is centrally located on the linear manifold tube290. FIG. 6 also illustrates an alternative pattern for the conduitsthat deliver fluid for evaporation. In the figure, five conduits 294,295, 296, 297 and 298, made from small bore plastic or silicone tubing,are attached at spaced locations on the linear manifold tube 290. Eachof these conduits is attached to the underside of the inflatable thermalblanket 120. While the conduits are shown in a straight line pattern, itshould be understood that other patterns could also be employed. In theconfiguration shown in FIG. 6, the orifices 300 of the fluiddistribution conduits are oriented to wet the entire body of the patient100, except the head area It should also be understood that the conduitscould be oriented to wet only selected parts of the body. As shown inFIG. 6, the numerous air apertures 217 will direct evaporative air toall portions of the patient's body where fluid is delivered by theconduits.

FIG. 7 illustrates another alternative construction for an inletmanifold and fluid delivery conduits. In this construction, the inletmanifold is a hub member 320 having a central fluid inlet and multipleradially oriented fluid outlets. The inlet line 262 extends through ahole formed in a central seal and attaches to a central inlet of the hub320. FIG. 7 also illustrates an alternative pattern for the conduits inwhich eight conduits 322, 323, 324, 325, 326, 327, 328 and 329 made fromsmall bore plastic or silicon tubing are attached to the radial outletsof the hub 320. Each of these conduits is attached to the underside ofthe inflatable thermal blanket 120. In the configuration shown in FIG.7, the orifices 330 of the fluid distribution conduits are oriented towet the entire body of the patient 100 except the head area. It shouldalso be understood that the conduits could be oriented to wet onlyselected parts of the body. As shown in FIG. 7, the numerous airapertures 217 will direct evaporative air to all portions of thepatient's body where fluid is delivered by the conduits.

The inventors contemplate modes of fluid delivery other than thetube-based embodiments that have been presented. For example, strips, orsheets, of hydrophilic material or wicking material could be used.

Preferably, the fluid distribution apparatus delivers the cooling fluidby depositing it directly on the skin the patient 100. However, theremay be times when direct application to the skin is disadvantageous. Forexample, if the fluid flow rate is not adequately controlled or if thecontours of the patient's body allow runoff, some of the fluid can poolunder the patient. This pooling of fluid is wasteful, messy and may beharmful to the skin laying in the pooled fluid for a prolonged time.Accordingly, as shown in FIG. 8, a layer of wicking material 350 may beloosely interposed between the underside of the inflatable thermalblanket 120 and its fluid distribution system, and the skin of thepatient 100. The wicking material 350 may be loosely attached to theinflatable thermal blanket 120 by connecting it at the peripheral edgesonly. The wicking material 350 may be any thin, loosely woven ornon-woven material. One example is a single layer of cotton gauzematerial. The wicking material 350 serves to keep the fluid on the skinarea where it is deposited, by minimizing run-off.

If a low fluid supply pressure is desirable, the fluid reservoir 260 canbe elevated above the level of the inflatable thermal blanket 120 suchthat fluid pressure is generated by gravity. This configuration is shownin FIG. 1. If higher fluid supply pressures are desired, a pump 360 maybe employed, as shown in FIG. 9. The pump 360 is interposed in the fluidsupply line 262. It may be provided using one of many IV fluid pumpsthat are generally available. Other pumps could also be employed. Forexample, the fluid reservoir 260 could be pressurized.

Preferably, the evaporative fluid used in the fluid distribution systemis water. However, other volatile fluids may also be used, or mixed withwater. For example, in high humidity environments the evaporativecooling effect of water is severely reduced. In these situations, it maybe desirable to use a different volatile fluid such as a mixture ofalcohol and water. Other volatile, non-toxic fluids could be substitutedor mixed with water to provide the desired evaporative characteristics.These fluid combinations may be premixed and supplied in sealedcontainers for convenience or may be mixed by the therapy provider.

In addition to inflatable thermal blankets shaped to various partialportions and combinations of the patient's trunk and limbs, specializedblanket configurations for various body parts may also be constructed.FIGS. 10, 11 and 12 illustrate an inflatable thermal blanket formed as athermal helmet 400 constructed to fit over the head 402 of a patient404. The helmet 400 is constructed in similar fashion to the inflatablethermal blanket 120. Thus, it has a base sheet 410 and an upper sheet412 that are joined together by a continuous air-impervious heat seal atthe periphery thereof, and optionally attached at interior portionsthereof with heat seals, to define an inflatable structure 414. The basesheet 410 is provided with a plurality of apertures 416. The helmet 400is inflated with air delivered by an airhose 420. This air is exhaustedtoward the patient's head 402 through the apertures 416. Thus, thehelmet 400 has a component for cooling the patient 404 convectively. Italso has an evaporative component that includes a conduit 430 made fromsmall bore plastic tubing or the like. The conduit 430 is attached tothe underside of the helmet 400, and is arranged in serpentine fashion.The conduit 430 extends through a hole in the helmet 400, and connectsto an inlet line 432, via a connector 434. The inlet line 432 isconnected to a fluid supply reservoir (not shown), and delivers acooling fluid to the conduit 430. The conduit 430 is provided withmultiple orifices 436, shown in FIG. 12 as spray nozzles. Alternatively,slits or holes could also be used to provide the orifices.

Advantageously, the regions of the patient's body that receive thecombined evaporative-convective cooling in accordance with the inventioncan be selected by the care giver. The volume of fluid delivered can becontrolled to either be fully evaporated, or to be in excess, and thusbe delivered to body areas which are at various distances from theorifices. Optionally, an incorporated liquid sensing device could beused to determine and control the rate of delivery of the fluid forevaporation.

The fluid distribution apparatus thus allows fluid to be distributed anddelivered to desired portions of the patient's body, at a controlledrate, over a prolonged period of time, without requiring the inflatablethermal blanket to be lifted or frequent operator involvement. While theinflatable thermal blankets illustrated herein are shown in particularshapes and sizes, it will be recognized that because different patientshave different shapes and sizes, different shapes and sizes ofinflatable thermal blankets may be made available to accommodate mostpatients.

Other embodiments and modifications of this invention may occur to thoseof ordinary skill in the art in view of these teachings. Therefore, thisinvention is to be limited only by the following claims, which includeall such embodiments and modifications when viewed in conjunction withthe above specification and accompanying drawings.

We claim:
 1. An apparatus for cooling a patient, comprising: an uppersheet and a base sheet connected together at a plurality of locations toform a convective device; an air inlet in the convective device fordelivering pressurized air; a plurality of apertures opening through thebase sheet for exhausting the pressurized air from the convectivedevice; and an evaporative cooling element adapted to be disposedbeneath the base sheet.
 2. The apparatus of claim 1, wherein theevaporative cooling element includes one or more conduits, a fluid inletconnected to one or more conduits, and a plurality of orifices in theone or more conduits.
 3. The apparatus of claim 2, wherein the conduitscomprise plastic tubing.
 4. The apparatus of claim 2, wherein theconduits comprise silicone tubing.
 5. The apparatus of claim 2 whereinthe orifices are holes in the conduits.
 6. The apparatus of claim 2wherein the orifices are slits in the conduits.
 7. The apparatus ofclaim 2 wherein the orifices are nozzles on the conduits.
 8. Theapparatus of claim 2, wherein the orifices are holes in the ends of theconduits.
 9. The apparatus of claim 2, wherein the fluid inlet is adistribution manifold that connects to multiple ones of the conduits.10. The apparatus of claim 2, further including wicking material adaptedto be disposed against the evaporative cooling element beneath the fluiddelivery apparatus.
 11. The apparatus of claim 10, wherein the wickingmaterial is made from a woven material.
 12. The apparatus of claim 10,wherein the wicking material is made from a non-woven material.
 13. Theapparatus of claim 10, wherein the wicking material is loosely attachedto the convective device.
 14. A system for cooling a patient,comprising: a source of a flow of temperature-controlled air; aconvective device including an upper sheet and a base sheet connectedtogether at a plurality of locations; an air inlet in the convectivedevice for delivering a flow of temperature-controlled air into theconvective device; an air hose connecting the air source to the airinlet; the base sheet including means for exhaustingtemperature-controlled air from the convective device to convectivelycool the patient; and a fluid delivery apparatus adapted to exhaustfluid to evaporatively cool the patient.
 15. The system of claim 14,wherein the fluid delivery apparatus includes one or more conduits andone or more orifices in each of the one or more conduits.
 16. The systemof claim 15, wherein the conduits comprise plastic tubing.
 17. Thesystem of claim 15, wherein the conduits comprise silicone tubing. 18.The system of claim 15 wherein the orifices are holes in the conduits.19. The system of claim 15 wherein the orifices are slits in theconduits.
 20. The system of claim 15 wherein the orifices are nozzles onthe conduits.
 21. The system of claim 15, wherein the orifices are holesin the ends of the conduits.
 22. The system of claim 15, wherein thedelivery apparatus includes a fluid inlet comprising a distributionmanifold that connects to multiple ones of the conduits.
 23. The systemof claim 15, further including wicking material adapted to be disposedagainst the fluid delivery apparatus.
 24. The system of claim 23,wherein the wicking material is made from a woven material.
 25. Thesystem of claim 23, wherein the wicking material is made from anon-woven material.
 26. The system of claim 23, wherein the wickingmaterial is attached to the convective device.
 27. The system of claim15, further including a fluid reservoir connected to the fluid deliveryapparatus and positioned above the convective device to supply fluid viagravity feed.
 28. The system of claim 27, further including a pumpconnected to the fluid delivery apparatus and to the reservoir to supplyfluid via mechanical pressurization.
 29. The system of claim 15, whereinthe fluid is water.
 30. The system of claim 15, wherein the fluid is avolatile liquid.
 31. The system of claim 14, wherein the means includeapertures through the base sheet.
 32. A method for convectively andevaporatively cooling a patient with a convective system, the convectivesystem including: a source of a flow of temperature-controlled air; aconvective device; an inlet in the convective device for delivering theflow of temperature-controlled air into the convective device; anairhose connecting the source to the inlet; means in the convectivedevice for exhausting temperature-controlled air from the convectivedevice; a fluid reservoir; and a fluid delivery apparatus adapted toexhaust fluid; the method including: placing the convective deviceadjacent one or more portions of the patient; providing a flow oftemperature-controlled air into the convective device; providing a fluidto the fluid delivery apparatus; convectively cooling the one or moreportions by exhausting air from the convective device; and evaporativelycooling the one or more portions by exhausting the fluid from the fluiddelivery apparatus.